My videotapes like everything else in my house in the woods seem to have mildew on them. Can I still play them or will the mildew clog up my VCR? And how do I get inside to clean the mildew off the sides or should I?
No, don’t play them. Youll certainly clog your vcr. I don’t know what to do with them. Toss them unless they are real important. You can open by taking out screws in the back.
In the future visit the hardware store & get some stuff to get rid of the moisture in the area you keep them. They make this DRid stuff, looks like snow, does the trick.
As for the VCR, I’d take it to a professional for cleaning, since you don’t want to risk electric shock. If it’s fairly old, replace it since new ones can be had for about $70-80. As for the tapes themselves, is the mildew INSIDE the tape housing? If so, you CAN take them apart, but you have to be careful not to lose any parts. A suggestion to prevent this in the future would be store the tapes in an airtight box (perhaps a cooler?) with packets of silica gel. Same goes for the VCR. Maybe an entertainment center that you seal off at the back.
Unfortunately, your tapes are toast (assuming the mildew is inside the housing, which seems extremely likely under the circumstances). Do not risk playing them, and I wouldn’t even bother trying to open them up to “clean” them–you won’t be able to get it all, and you risk damaging the tape even more. Unless they’re both important (personal value) and irreplaceable (a unique or master copy), I would toss them.
If you really need to clean them up, you’ll need to find a video specialist or film lab (which often handle videos now, too) in your area. There are plenty on the Internet as well which you can contact for rates and more specific advice regarding your collection.
Because mildew is a result of humidity, you are condemning all your other “good” tapes to the same fate unless you change/improve your storage environment. It is recommended that tapes not be exposed to an RH of more than 50% (although if it fluctuates a lot, this only worsens things), but obviously the lower the better. I’m not sure what you can do in your own specific home situation that isn’t just delaying the inevitable, but look on the bright side: videotapes are not considered by anyone a genuine archival medium, so they’re going to go sooner or later anyway. 
So if you need the tapes that bad, talk to a pro. In any case, sorry.